1. Field of the Invention
The present invention relates to an image processing apparatus, an imaging apparatus, and an image processing method.
2. Description of the Related Art
Conventionally, there is a known image processing apparatus that generates what is called a stroboscopic motion image, in which a plurality of images of an object in motion (hereinafter, described as a “moving object”) that are continuously captured by the imaging apparatus are combined in one image with a background so that the movement of the moving object can be seen at one view.
In general, the stroboscopic motion image is generated such that an image processing apparatus separates regions containing a moving object (hereinafter, described as “moving object regions”) from the rest region (hereinafter, described as a “background region”) and a plurality of images of the moving object regions are combined in one image containing the background region. The image processing apparatus of this type calculates differences between continuous images to separate between the moving object regions and the background regions to thereby separate the moving object regions from the background regions.
Furthermore, for example, there is a known image processing apparatus that uses the magnitude of a motion vector to separate between the moving object regions and the background regions (see, for example, Japanese Patent No. 3793258). The image processing apparatus eliminates background regions with motion vectors of small magnitudes, thereby extracting moving object regions with motion vectors of large magnitudes.
Therefore, even when the background regions contain an object, such as an audience or a tree in the outside, that does not stand still but moves slightly and intricately, it becomes possible to accurately extract the moving object regions by extracting the moving object regions containing a relatively large motion.
However, in the image processing apparatus as described above, a difference in the magnitude between the motion vectors is used to distinguish between the moving object regions and the background regions. Therefore, an extremely large number of calculation processes are needed to calculate the motion vectors. Consequently, processing time increases.
Furthermore, for example, if the image processing apparatus is mounted on a popular compact digital still camera (hereinafter, described as a “digital camera”), it takes even several tens of seconds to generate only one stroboscopic motion image, which is not appropriate for practical use.
Besides, when an image is captured by the digital camera held by hand, image blur may occur due to hand motion (camera shake) during image shooting. When the image blur occurs, the moving object regions and the background regions cannot completely be separated, and a part of the background regions may overlap the moving object regions resulting in an unnatural stroboscopic motion image.
Therefore, there is a need for an image processing apparatus, an imaging apparatus, and an image processing method capable of separating moving object regions from background regions simply and highly accurately to form one composite image even when continuous images contain image blur or the like due to hand motion (camera shake) during image shooting.